Cartridge case for a recoilless rifle



Nov. 14, 1961 w. A. MERDINYAN 3,008,412

CARTRIDGE CASE FOR A RECOILLESS RIFLE Filed Oct. 9, 1956 0 %QV\7B j) VQVV FIG. 2.

IN VEN TOR.

WILLIAM A. MERDINYAN.

u). a. 31W, aw. Qua H. 1. 3mm

ATTORNEYS.

Un fied m The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment of any royalty thereon.

This invention relates to cartridge cases for central nozzle type recoilless guns and has for an object to increase the ability of gas to pass laterally through cylinder walls of such case without unduly weakening such case and without permitting grains of the propelling charge explosive to fall out of the case during handling.

It has been common practice for the side walls of such a cartridge case to be provided with a plurality of generally circular perforations. Yet these sidewalls have been distorted and collapsed inwardly by gas pressure. In recoilless guns having a central nozzle much of the products of combustion of the propelling charge move radially outward in a forward portion of the cartridge case and then move again radially inward at a rear portion of the case near the central nozzle. These cartridge cases are usually stronger in tension to resist internal pressure than they are in compression and flexure to resist external pressure on the webs between holes, with the result that most failures are by inward collapse adjacent the nozzle entrance. The solution has not been as simple as providing larger perforations through which gas may pass. Rather it has been the problem of determining a maximum web of casing material between perforations simultaneously with a maximum perforate area. This problem has been complicated by the fact that best results have not been obtainable mathematically but only empirically.

One suggestion resided in having a plurality of circular openings graded in size. The results of this practice indicated that a maximum perforate area with maximum strength is not obtainable with circular openings. Another suggestion was the provision of elongated openings having rounded ends which (without being tested) seemed satisfactory from the standpoint of both strength and large perforate area. However, the elongated openings were believed to be unsatisfactory from the fact that the cylindrical shape grains of propelling charge carried in the cartridge case might fall out in handling. If grains should be blown out through the central nozzle the efficiency of a projectile would be lessened.

According to this invention, a rear end portion of a cartridge case for a recoilless gun of the central nozzle type is provided with at least two rows of generally triangularly shaped perforations, each of a size to include an area equivalent to that occupied by three of the circular perforations when spaced as in the forward part of the cartridge case. The webs between these perforations must be of a size to provide the requisite strength.

FIG. 1 is a perspective of forward and rear portions of a cartridge case containing the embodiment of FIG. 3.

FIG. 2 is a developed plan view of a rear portion of a cartridge case embodying the present invention.

FIG. 3 is likewise a developed view of a rear portion of a preferred cartridge case.

FIG. 4 is also a developed view of a rear end portion of a cartridge case embodying another type of the present invention.

The rear portion of the cartridge case of FIG. 1 has the present invention embraced within the bracket A and disclosed more in detail in the preferred embodiment shown in FIG. 3. Only front and rear portions are shown in atent ICQ . case for these recoilless guns. The larger holes are spaced apart a distance equal to what would be the case if it were imagined one of these small holes were arranged at each vertex of the large holes. Stated in another way, the large holes are of a size and spacing as would result if it were imagined one of the small holes were originally in a vertex of these triangles and the metal between the enclosed three small holes were removed. The web 16 is strengthened at a mid portion 15 where adjacent webs intersect to provide greater strength. Each of these webs is of a size such as would result if the same spacing between the small holes were maintained.

In FIG. 3, the same numerals designate similar parts except that the numerals in FIG. 3 have the exponent a. The large holes are thus slightly differently arranged. This is the preferred embodiment because it is easier to punch when the apices of the holes in a circumferential row are in the same general location, and also because the web material, being more nearly uniform in FIG. 3, is easier to resize and reform after becoming distorted in forming.

In FIG. 4, similar parts bear similar reference numerals to what they do in FIGS. 2 and 3 except that in FIG. 4 the reference numerals have the exponent b attached.

Among the advantages of this invention may be mentioned that the arrangement of larger holes provides approximately 60% more flow area in a critical section for the powder gases in the central nozzle-type gun to include an area equivalent to that occupied by three of the circular perforations in the forward part of the cartridge case. The webs between these perforations must be of a size to provide the requisite strength. The triangular holes are less likely to permit grains of propellant to fall out in handling than are elongated holes of equivalent area. One cartridge case in which the present invention has been employed was 3 /8 inches outside diameter. The spacing between centers longitudinally of the cartridge case in FIG. 3 was .306 inch for both the round and triangular holes with the round holes being about .250 inch in diameter.

I claim:

1. In a cartridge case for a central nozzle type recoilless gun in which a large portion of the surface of said case is provided with rows of generally circular and uniformally spaced perforations, the combinations therewith of the improvement for reducing the danger of said cartridge case becoming distorted in shape in rear portions, said improvement comprising at least two rows of perforations adjacent the rear end portion of said case, each row having perforations which are larger than the circular perforations and are of generally triangular shape and are each of a size large enough to be cap-able of including at least three adjacent similarly spaced circular portions when said circular perforations are located at the vertices of said generally triangular perforations, whereby the webs of imperforate material between said large perforations have not been substantially reduced, the gas through said large perforations has been increased, yet generally cylindrical grains of propelling charge are restrained from falling out.

2. A cartridge case according to claim 1 in which there are at least two rows of said large perforations, the adjacent vertices of the large perforations in each row and the adjacent sides of the large perforations in each row being longitudinally opposite each other.

3. A cartridge case according to claim 1 in which there Patented Nov. 14, 1961 arei at. least two rowsof. large. p rforationsrand. port ons, of the perforations in each row longitudinally overlap portions of the perforations in another row.

' A. c m g a e or ing laiml; Vin-.whi ht em;

are at least .two 1 rows of.;iarge perforations; withya zlq srtzz 5 one of..the small. perforations heingbetwerengeaeh pf the largeperforations, in: each row-and without anyisnlgstarltia1 changeibeing made in, size of theawebs "or imperforate; materiaibetween perforations.;-

5; A cartridge caseaccordingtoclaim l -in;; vhichrthq ie. 10

re .atr i estttwor rows fi sa d e. mtf setiprneefiheaslie: cent vertices of the large perforations in each'row and adjacent sides of the large perforations being transversely opposite one an'otherl Reference-s gned in h file r' hi :pa enti 1 a D; STATES PA EN S:

2,535,624 But-he L V ne 26,1950 2,703,529 r Tuckerman eta1. Mar. 8,1955 

